The subject matter disclosed herein relates to the art of rotary wing aircraft and, more specifically, to drive systems for rotary wing aircraft.
In typical rotary winged aircraft, for example, helicopters, one or more engines are utilized to drive a main rotor assembly, and a tail rotor located at an extending tail of the helicopter. A tail rotor shaft assembly is utilized to connect the tail rotor to the main transmission, thereby connecting it to the engine, and typically includes multiple shaft sections connected by flexible couplings and supported by bearings mounted in housings and attached to the airframe, known as hanger bearings. The flexible couplings transmit torque from one shaft segment to the next shaft segment, while the hanger bearings support the shaft segments and provide axial and angular compliance.
During operation of the helicopter, the airframe along the extending tail will deflect, thus requiring deflection of the shaft assembly, along the same curvature of the airframe deflection. Commonly, hanger bearings utilize soft rubber supports or an additional spherical element to achieve the required compliance, but these additional parts require periodic inspection and regular maintenance. The hanger bearings must operate under conditions of rotational misalignment and axial tension between adjacent segments to accommodate assembly variations and airframe deflections. These displacements and their resultant loads quickly damage the typical hanger bearing, increasing maintenance and repair required. Traditional designs utilize ball bearings mounted in rubber bushings that allow for limited deflections, reducing but not eliminating the generated loads.